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Watch: Boston but also NYC, Oklahoma City, Atlanta, Spokane

"Nothing like this has ever happened at the finish line of the Boston Marathon on Patriots Day in Boston," msnbc's Rachel Maddow said on Monday night.

"Nothing like this has ever happened at the finish line of the Boston Marathon on Patriots Day in Boston," msnbc's Rachel Maddow said on Monday night. "But it's not like we as a country have no experience of people setting off bombs to kill and maim civilians, and to instill terror in us all."

Monday's explosions at the finish line of the Boston Marathon are the latest incident in the list of attacks by explosive devices in America during the past 20 years. In most of the cases, the causes took a significant amount of time to determine. But in each event, the devices were planted by different people, for different reasons, for different effects.

Included in the list are the bombings in an Oklahoma City federal building, at a Martin Luther King Jr. parade in Washington, in front of a New York City recruiting office, and at Centennial Olympic Park during the summer Olympic games in Atlanta.